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Revert "cpuset: Make cpuset hotplug synchronous"

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This reverts commit 1599a185f0.

This and the previous commit led to another circular locking scenario
and the scenario which is fixed by this commit no longer exists after
e8b3f8db7a ("workqueue/hotplug: simplify workqueue_offline_cpu()")
which removes work item flushing from hotplug path.

Revert it for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2017-12-04 14:41:11 -08:00
parent 52cf373c37
commit 11db855c3d
4 changed files with 32 additions and 22 deletions
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6
include/linux/cpuset.h
View file

@ -52,7 +52,9 @@ static inline void cpuset_dec(void)
extern int cpuset_init(void);
extern void cpuset_init_smp(void);
extern void cpuset_force_rebuild(void);
extern void cpuset_update_active_cpus(void);
extern void cpuset_wait_for_hotplug(void);
extern void cpuset_cpus_allowed(struct task_struct *p, struct cpumask *mask);
extern void cpuset_cpus_allowed_fallback(struct task_struct *p);
extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
@ -165,11 +167,15 @@ static inline bool cpusets_enabled(void) { return false; }
static inline int cpuset_init(void) { return 0; }
static inline void cpuset_init_smp(void) {}
static inline void cpuset_force_rebuild(void) { }
static inline void cpuset_update_active_cpus(void)
{
partition_sched_domains(1, NULL, NULL);
}
static inline void cpuset_wait_for_hotplug(void) { }
static inline void cpuset_cpus_allowed(struct task_struct *p,
struct cpumask *mask)
{

45
kernel/cgroup/cpuset.c
View file

@ -2277,8 +2277,15 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs)
mutex_unlock(&cpuset_mutex);
}
static bool force_rebuild;
void cpuset_force_rebuild(void)
{
force_rebuild = true;
}
/**
* cpuset_hotplug - handle CPU/memory hotunplug for a cpuset
* cpuset_hotplug_workfn - handle CPU/memory hotunplug for a cpuset
*
* This function is called after either CPU or memory configuration has
* changed and updates cpuset accordingly. The top_cpuset is always
@ -2293,7 +2300,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs)
* Note that CPU offlining during suspend is ignored. We don't modify
* cpusets across suspend/resume cycles at all.
*/
static void cpuset_hotplug(bool use_cpu_hp_lock)
static void cpuset_hotplug_workfn(struct work_struct *work)
{
static cpumask_t new_cpus;
static nodemask_t new_mems;
@ -2351,31 +2358,25 @@ static void cpuset_hotplug(bool use_cpu_hp_lock)
}
/* rebuild sched domains if cpus_allowed has changed */
if (cpus_updated) {
if (use_cpu_hp_lock)
rebuild_sched_domains();
else {
/* Acquiring cpu_hotplug_lock is not required.
* When cpuset_hotplug() is called in hotplug path,
* cpu_hotplug_lock is held by the hotplug context
* which is waiting for cpuhp_thread_fun to indicate
* completion of callback.
*/
mutex_lock(&cpuset_mutex);
rebuild_sched_domains_cpuslocked();
mutex_unlock(&cpuset_mutex);
}
if (cpus_updated || force_rebuild) {
force_rebuild = false;
rebuild_sched_domains();
}
}
static void cpuset_hotplug_workfn(struct work_struct *work)
{
cpuset_hotplug(true);
}
void cpuset_update_active_cpus(void)
{
cpuset_hotplug(false);
/*
* We're inside cpu hotplug critical region which usually nests
* inside cgroup synchronization. Bounce actual hotplug processing
* to a work item to avoid reverse locking order.
*/
schedule_work(&cpuset_hotplug_work);
}
void cpuset_wait_for_hotplug(void)
{
flush_work(&cpuset_hotplug_work);
}
/*

2
kernel/power/process.c
View file

@ -204,6 +204,8 @@ void thaw_processes(void)
__usermodehelper_set_disable_depth(UMH_FREEZING);
thaw_workqueues();
cpuset_wait_for_hotplug();
read_lock(&tasklist_lock);
for_each_process_thread(g, p) {
/* No other threads should have PF_SUSPEND_TASK set */

1
kernel/sched/core.c
View file

@ -5624,6 +5624,7 @@ static void cpuset_cpu_active(void)
* restore the original sched domains by considering the
* cpuset configurations.
*/
cpuset_force_rebuild();
}
cpuset_update_active_cpus();
}